| Aquaculture |
| Volume 341, Number 5 (March 2012) |
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Effects of stocking density and sustained aerobic exercise on growth, energetics and welfare of rainbow trout |
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Authors: |
D.J. McKenzie, E. Höglund, A. Dupont-Prinet, B.K. Larsen, P.V. Skov, P.B. Pedersen, A. Jokumsen |
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Author Affiliations: |
| no affiliations available |
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Source: |
Aquaculture, Volume 341, Number 5 (March 2012) |
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Page Numbers: |
216 – 222 |
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Available Full Text: |
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Publisher’s Site |
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Abstract: |
Two stocking densities, “low” (L, between ~19 and ~25kgm-3) and “high” (H, between ~75 and ~100kgm-3) were compared for effects on specific growth rate (SGR), feed conversion, energetics and welfare of rainbow trout reared at 14°C either in static water (S) or swimming in a gentle current of ~0.9 bodylengths s-1(C). Trout (initial mass ~110g) were reared for 9weeks in circular tanks (volume 0.6m3), in triplicate of four conditions (LS, LC, HS, HC). Fish were fed ad-libitum daily; waste pellets were swirl-collected at the outflow to calculate feed intake. SGR was measured each three weeks for the last six weeks of the trial. The tanks functioned as intermittent-stopped flow respirometers, to permit metabolic rate to be measured as instantaneous oxygen uptake once per hour. Mean (±SD) SGR was significantly lower at H than L (1.51±0.03 vs1.44±0.04% day-1, respectively, n=6) and lowest in HC. When compared over a similar interval of mass gain, H groups had approximately 25% higher metabolic rates than L, with the highest rates in the HC condition. As a result, fish in the H groups dissipated a greater amount of feed energy as metabolism and, across all groups, there was a direct negative relationship between the quantity of energy dissipated and their SGR. There was no evidence of a neuroendocrine stress response, plasma cortisol was around 1ngml-1in all conditions. An acute crowding stress increased plasma cortisol to above 120ngml-1in all groups, but C groups recovered to control levels within 8h whereas S groups required 20h. Respirometry on individuals revealed that H fish had approximately 14% higher metabolic rates than L fish, indicating that increased metabolic rate in rearing tanks was in part physiological. The H groups had approximately 15% lower critical swimming speeds than the L groups which, together with their raised metabolic rate, indicated a physiological impairment. Thus, high density reduced SGR by raising energy dissipation, at least partially as a physiological response by the fish, although there was no evidence of an endocrine stress response. The only beneficial effect of C was in recovery from acute stress. |
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Citation: |
D.J. McKenzie, E. Höglund, A. Dupont-Prinet, B.K. Larsen, P.V. Skov, P.B. Pedersen, A. Jokumsen . Effects of stocking density and sustained aerobic exercise on growth, energetics and welfare of rainbow trout. Aquaculture, Volume 341, Number 5 (March 2012), pp. 216-222, <http://ejournals.ebsco.com/direct.asp?ArticleID=4D9DBDAC247D45807360> |
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URL: |
http://ejournals.ebsco.com/direct.asp?ArticleID=4D9DBDAC247D45807360 |
